Studies in the past decade have established the detrimental effect of marijuana on the immune functions of mononuclear cells in vitro. Antibody formation by B cells, T and B cell mitogenic responses, cytokine induction from T cells and macrophages, macrohage phagocytosis and NK cell activity against tumor cells have all been reported to be depressed by delta-9- tetrahydroxycannabinol (THC) and 11-OH THC, which constitute the primary psychoactive components of marijuana. However, no detailed study of THC modulation of polymorphonuclear neutrophil (PMN) function has yet been reported. We propose to evaluate the effect of THC on PMN function against Candida albicans which causes one of the most common opportunistic infections in AIDS patients. We recently found that a complex interaction of NK cells and PMN takes place to control C. albicans growth in vitro. Using a 24 hr 3H-glucose assay that we developed, we found that human PMN could efficiently inhibit Candida growth. Human NK cells did not have direct antifungal activity but they could respond to C. albicans by releasing cytokines such as interferon gamma (IFNg), tumor necrosis factor (TNF) and an as yet unidentified factor, all of which are able to activate PMN function. This proposal is to study the effect of 9- THC and 11-OH THC on the antifungal activity of PMN from normal individuals and on the interaction of NK cells with PMN to affect Candida growth. THC will be added at various concentrations for 1-6 hr to PMN before they are tested for antifungal activity. These treated cells will also be washed to ascertain if the effect seen is reversible. PMN, inhibited maximally under optimal conditions will then be assessed for oxidative and non-oxidative metabolic activities to determine which biochemical pathways are susceptible to THC. Because NK cells activity against tumor cells are readily inhibited by THC, it is predicted that cytokine production by NK cells in response to Candida will also be affected. NK cells, treated with graded doses of THC for 1-6 hr will be stimulated with C. albicans and assessed for IFNg, TNF and the newly-described PMN activating factor. We will also determine in NK cells that are first stimulated with Candida are more resistant to inhibition with THC. Finally, we intend to examine if cytokines can reverse the inhibitory effect of THC on PMN. The results from these studies will provide new information on THC modulation of PMN function and also on the effect of THC on C. albicans immunity, which might help in treatment of AIDS patients infected with this organism.